Stretch film is widely used for wrapping and securing pallet loads for shipping. This is due to the fact that stretch film exhibits a “memory”, or a tendency to shrink, upon stretching. For example, stretch film that is stretched by an amount of 10% will shrink nearly 10% of its stretched length. This “memory” assists in securing wrapped palletized articles together under compression.
Stretch film is fabricated in the form of stretch film rolls. Each stretch film roll may be used to manually wrap a pallet load, or may be loaded into an automated wrapping machine.
An issue with conventional stretch film rolls is that the stretch film wound within the roll can become damaged if the stretch film roll is dropped or otherwise mishandled. For example, dropping the stretch film roll on its edge can result in tearing of the stretch film during wrapping of a pallet load.
One approach to avoiding such tearing involves folding the longitudinal edges of the stretch film prior to winding, so as to provide a stretch film having reinforced longitudinal edges within the stretch film roll. Methods of folding the longitudinal edges of stretch film prior to winding have been described. For example, U.S. Pat. No. 5,520,872 to Scherer discloses a strip of stretch-wrap material having flat, double thickness hems at opposite margins thereof. The hemmed strip is formed on an apparatus including a first roller having a width less than the width of stock material, whereby opposite margins of the stock material project beyond opposite ends of the roller, and a second roller for guiding the strip at an acute angle from the first roller for causing opposite marginal portions to fold. The strip is maintained under tension by a take-up roller or other means, and guide bars are provided for further folding the marginal portions past 90 degree angles so that they continue to be folded inwardly against the main body of the strip.
Another approach to avoiding tearing involves oscillating the stretch film during winding, so as to prevent formation of hard edges within the stretch film roll. Methods of oscillating stretch film during winding have been described. For example, U.S. Pat. No. 5,967,437 to Martin-Cocher et al. discloses a method of manufacturing rolls of pre-stretched film that comprises importing oscillation to the film with a component perpendicular to the film axis. During pre-stretching and winding of the film on a take-up roll, a feed roll, namely a spool from which the stretchable film for stretching is taken, is caused to oscillate, and/or the take-up core is caused to oscillate.
Improvements are generally desired. It is therefore an object at least to provide a novel method and apparatus for fabricating stretch film rolls.